Germination of Seeds

A ejaculate consists essentially of a set out coat, stored food and a young plant, the embryo. The seed downed player coat whitethorn be made of inner tegmen and outer testa. On the seed coat a scar (hilum) is present which shows the place of attachment of a seed in the fruit is present. At one end of the hilum is the micropyle. Through micropyle the seed absorbs water during the process of germination. The embryo consists of epicotyl,one or two seed leaves called cotyledons, and a hypocotyle. The portion of the embryo higher up the point of attachment of cotyledons to embryo axis, and down the stairs the plumule is called epicotyl.The plumule forms shoot. the portion of the embryo below the point of attachment of cotyledons to embryo axis but above the radicle, is called hypocotyls. The radicle forms steady down. The seed as well as contain the food, derived from the endosperm tissue. The food may remain as such or may be digested and stored in the cotyledons. Thus the coty ledons become thick due to the presence of stored food. This food is supplied to the development plant during the process of germination of seeds. In the grain of corn whiskey, the cotyledon is modify into an organ called scutellum a term that comes from the Latin word meaning resistance.The food stored in scutellum is used first during germination of seed. Later on scutellum absorbs the food of endosperm and supply it to the developing embryo. The gamboge grain is infact a ace seeded fruit in which seed coat fruit fence is fused. Practical Work probe structure of seed of gram and lemon yellow With the do of hand lens locate micropyle and hilum of the two seeds. With the help of scalpel cut the seeds longitudinally and observe different parts of the embryo along with endosperm with the help of (fig 16. 1) 1. What is the function of micropyle? 2. Why cant you find endosperm in gram seed? Fig. 16. 11 Structure of seed of gram (a) and maize grain (b) 16. 5. 1 Seed germinatio n During germination ( emergence and development) of a seed the water is absorbed through micropyle, and the formerly dormant embryo resumes growth and emerges from the seed. The root is normally the first structure emerging the seed, growing chop-chop and absorbing water and minerals from the soil. Much of the water is transported to the cells in embryo.As its cells extend the stem pushes out of the soil. There are two types of germination, epigeal and hypogeal. When the cotyledons appear above Fig 16. 12 (a) Hypogeal germination in gram seed the reason by the elongation of hypocotyl, the type of seed germination is called epigeal, e. g. seeds of melons, cucumber and beansFig 16. 12(b). 16. 12 (b) Epigeal germination in bean seed When the cotyledons remain below the soil, and epicotyl elongates rescue only plumule above the soil surface, it is described as hypogeal germination, e. g. eed of gram and maize grainFig 16. 12(a) Germination is the onset of growth of a seed, often lo llowing a head of dormancy, in response to suitable environmental conditions. 16. 5. 2 Conditions For germination to restoration place the seed must be viable (living) and should go through adequate food for its germination. The following environmental conditions must exist. In some seeds such as of tobacco plant light is also necessary to depart germination of seeds (i) Moisture or water (ii) Air(O2) (iii) adequate temperature (i) Moisture or waterThrough micropyle, the seed absorbs water, which swells it causing the seed coat to burst. This helps the root to emerge out of seed. Water absorbed by the germination seed helps to activate the enzymes to digest the food of seed, which is made available to the growing embryo. It also helps to elongate hypocotyls and epicotyl, to grow out. (ii) Air Because oxidative metabolism usually takes oer soon after a plant embryo starts to grow, most seeds gather up oxygen for germination. So air is very important for germination as it contai ns to the highest degree 21% of oxygen, which is used during respiration. iii)Suitable temperature Germination of seeds occur over a wide temperatue range betwixt 5-30 C. the optimum temperature for the germination of seeds of most plants ranges between 25-30 C. optimum or suitable temperature is necessary for the enzymes to function. During early germination of seeds, the springy mobilization of food reserves stored in the embryo cotyledons or the endosperm is arbitrate by hormones, which in some cases are gibberellins. Practical work investigating the conditions necessary for germinationSet up four test tybes each(prenominal) with ten seeds labeled A, B, C and D as shown in Fig. 16. 13. instal undergrounds A, C and Din a warm place, in laboratory, Put tube B in a refrigerator. The test tube will have the following environmental conditions Water, suitable temperature and air Water and the air (low temperature) Suitable temperature and air Water and suitable temperature (no a ir) Observe the test tubes regularly for about one week. 1. In which tubes the seeds germinate? 2. Did all the seeds in these tubes germinate, if not, why? bring in the conditions necessary for the germination of seeds?